Method of forming low profile wire bonds between integrated circuits dies and printed circuit boards

ABSTRACT

A method of profiling a series of wire bonds between a line of contact pads on a die, and a corresponding set of conductors on a supporting structure, by electrically connecting each of the contact pads on the die to a corresponding conductor on the supporting structure with a respective wire bond, each of the wire bonds extending in an arc from the contact pad to the conductor, and, pushing on each of the wire bonds individually to collapse the arc and plastically deform the wire bond such that the plastic deformation maintains the wire bond in a flatter profile shape.

The present application is a Continuation-In-Part of U.S. Ser. No. 11/860,539 (Our Docket MPN008US), filed Sep. 25, 2007, the contents of which are incorporated herein by cross reference.

FIELD OF THE INVENTION

The invention relates to the field of integrated circuits. In particular, the invention is directed to the wire bonds between a circuit board and the contact pads on the integrated circuit die.

CO-PENDING APPLICATIONS

The following application has been filed by the Applicant simultaneously with the present application:

MPN016US MPN017US MPN018US

The disclosure of this co-pending application is incorporated herein by reference. The above application has been identified by its filing docket number, which will be substituted with the corresponding application number, once assigned.

CROSS REFERENCES TO RELATED APPLICATIONS

Various methods, systems and apparatus relating to the present invention are disclosed in the following US Patents/Patent Applications filed by the applicant or assignee of the present invention:

6276850 6520631 6158907 6539180 6270177 6405055 6628430 6835135 6626529 6981769 7125338 7125337 7136186 7286260 7145689 7130075 7081974 7177055 7209257 6443555 7161715 7154632 7158258 7148993 7075684 10/943905 10/943906 10/943904 10/943903 10/943902 6966659 6988841 7077748 7255646 7070270 7014307 7158809 7217048 11/225172 11/255942 11/329039 11/329040 7271829 11/442189 11/474280 11/483061 11/503078 11/520735 11/505858 11/525850 11/583870 11/592983 11/592208 11/601828 11/635482 11/635526 10/466440 7215441 11/650545 11/653241 11/653240 7056040 6942334 11/706300 11/740265 11/737720 11/739056 11/740204 11/740223 11/753557 11/750285 11758648 11/778559 11834634 11/838878 11845669 12015407 12/017331 12030823 6799853 7237896 6749301 10/451722 7137678 7252379 7144107 10/503900 10/503898 10/503897 7220068 7270410 7241005 7108437 7140792 10/503922 7224274 10/503917 10/503918 10/503925 10/503927 10/503928 10/503929 10/503885 7195325 7229164 7150523 10/503889 7154580 6906778 7167158 7128269 6688528 6986613 6641315 7278702 10/503891 7150524 7155395 6915140 6999206 6795651 6883910 7118481 7136198 7092130 6786661 6808325 10/920368 10/920284 7219990 10/920283 6750901 6476863 6788336 6322181 6597817 6227648 6727948 6690419 10/470947 6619654 6969145 6679582 7328896 6568670 6866373 7280247 7008044 6742871 6966628 6644781 6969143 6767076 6834933 6692113 6913344 6727951 7128395 7036911 7032995 6969151 6955424 6969162 10/919249 6942315 11/006577 7234797 6986563 7295211 11/045442 7286162 7283159 7077330 6196541 7303257 11/185725 7226144 11/202344 7267428 11/248423 11/248422 7093929 11/282769 11/330060 11/442111 7290862 11/499806 11/499710 6195150 11749156 11782588 11/854435 11/853817 11/935958 11924608 6362868 11970993 12031526 6831681 6431669 6362869 6472052 6356715 6894694 6636216 6366693 6329990 6459495 6137500 6690416 7050143 6398328 7110024 6431704 6879341 6415054 6665454 6542645 6486886 6381361 6317192 6850274 09/113054 6646757 6624848 6357135 6271931 6353772 6106147 6665008 6304291 6305770 6289262 6315200 6217165 6496654 6859225 6924835 6647369 6943830 09/693317 7021745 6712453 6460971 6428147 6416170 6402300 6464340 6612687 6412912 6447099 6837567 6505913 7128845 6733684 7249108 6566858 6331946 6246970 6442525 09/517384 09/505951 6374354 7246098 6816968 6757832 6334190 6745331 7249109 7197642 7093139 10/636263 10/636283 10/866608 7210038 10/902883 10/940653 10/942858 11/706329 11/757385 11/758642 7119836 7283162 7286169 10/636285 7170652 6967750 6995876 7099051 7172191 7243916 7222845 11/239232 7285227 7063940 11/107942 7193734 7086724 7090337 7278723 7140717 11/190902 11/209711 7256824 7140726 7156512 7186499 11/478585 11/525862 11/540574 11/583875 11/592181 6750944 11/599336 7291447 11744183 11/758646 11/778561 11/839532 11/838874 11/853021 11/869710 11/868531 11927403 11951960 12019556 10/636225 6985207 6773874 6650836 7324142 10/636224 7250975 7295343 6880929 7236188 7236187 7155394 10/636219 10/636223 7055927 6986562 7052103 7312845 10/656281 10/656791 10/666124 10/683217 7289142 7095533 6914686 6896252 6820871 6834851 6848686 6830246 6851671 10/729098 7092011 7187404 10/729159 10/753458 6878299 6929348 6921154 10/780625 10/804042 6913346 10/831238 10/831237 10/831239 10/831240 10/831241 10/831234 10/831233 7246897 7077515 10/831235 10/853336 10/853117 10/853659 10/853681 6913875 7021758 7033017 7161709 7099033 7147294 7156494 11/012024 11/011925 7032998 7044585 7296867 6994424 11/006787 7258435 7097263 7001012 7004568 7040738 7188933 7027080 7025446 6991321 7131715 7261392 7207647 7182435 7097285 7331646 7097284 7083264 7147304 7232203 7156498 7201471 11/501772 11/503084 11/513073 7210764 11/635524 11/706379 11/730386 11/730784 11/753568 11/782591 11/859783 12015243 12037069 6710457 6775906 6507099 7221043 7107674 7154172 11/442400 7247941 11/736540 7307354 11/940304 6530339 6631897 6851667 6830243 6860479 6997452 7000913 7204482 11/212759 11/281679 11/730409 6238044 6425661 11/003786 7258417 7293853 7328968 7270395 11/003404 11/003419 7334864 7255419 7284819 7229148 7258416 7273263 7270393 6984017 11/003699 11/071473 7156497 11/601670 11748482 11/778563 11/779851 11/778574 11/853816 11/853814 11/853786 11/872037 11/856694 11965703 11971170 12023011 12036896 11/003463 11/003701 11/003683 11/003614 7284820 7341328 7246875 7322669 11/764760 11853777 11955354 12022994 11/293800 11/293802 11/293801 11/293808 11/293809 11/482975 11/482970 11/482968 11/482972 11/482971 11/482969 6431777 6334664 6447113 7239407 6398359 6652089 6652090 7057759 6631986 7187470 7280235 11/501775 11744210 11/859784 6471331 6676250 6347864 6439704 6425700 6588952 6626515 6722758 6871937 11/060803 11/097266 7328976 11/685084 11/685086 11/685090 11/740925 11/763444 11/763443 11946840 11961712 12/017771 7249942 7206654 7162324 7162325 7231275 7146236 7278847 10/753499 6997698 7220112 7231276 10/753440 7220115 7195475 7144242 7306323 7306319 11/525858 7322674 11/599335 11/706380 11736545 11/736554 11/739047 11749159 11/739073 11/775160 11/853755 11/940291 11934071 11951913 6786420 6827282 6948661 7073713 10/983060 7093762 7083108 7222799 7201319 11/442103 11/739071 11/518238 11/518280 11/518244 11/518243 11/518242 7032899 6854724 7331651 7334870 7334875 11/357296 11/357298 11/357297 12015479 12/017270 12015218 6350023 6318849 6592207 6439699 6312114 11/246676 11/246677 11/246678 11/246679 11/246680 11/246681 11/246714 11/246713 11/246689 11/246671 11/246670 11/246669 11/246704 11/246710 11/246688 11/246716 11/246715 11/246707 11/246706 11/246705 11/246708 11/246693 11/246692 11/246696 11/246695 11/246694 11/482958 11/482955 11/482962 11/482963 11/482956 11/482954 11/482974 11/482957 11/482987 11/482959 11/482960 11/482961 11/482964 11/482965 11/482976 11/482973 11/495815 11/495816 11/495817 60992635 60992637 60992641 10/803074 10/803073 7040823 10/803076 10/803077 10/803078 10/803079 10/922971 10/922970 10/922836 10/922842 10/922848 10/922843 7125185 7229226 11/513386 11/753559 10/815621 7243835 10/815630 10/815637 10/815638 7251050 10/815642 7097094 7137549 10/815618 7156292 11738974 10/815635 10/815647 10/815634 7137566 7131596 7128265 7207485 7197374 7175089 10/815617 10/815620 7178719 10/815613 7207483 7296737 7270266 10/815614 7314181 11/488162 11/488163 11/488164 11/488167 11/488168 11/488165 11/488166 7267273 11/834628 11/839497 11/944449 10/815636 7128270 11/041650 11/041651 11/041652 11/041649 11/041610 11863253 11863255 11/863257 11863258 11863262 11/041609 11/041626 11/041627 11/041624 11/041625 11863268 11863269 11863270 11863271 11863273 76584733 11/041556 11/041580 11/041723 11/041698 11/041648 11863263 11863264 11863265 11863266 11863267 10/815609 7150398 7159777 10/815610 7188769 7097106 7070110 7243849 7314177 11/480957 11/764694 11957470 6227652 6213588 6213589 6231163 6247795 6394581 6244691 6257704 6416168 6220694 6257705 6247794 6234610 6247793 6264306 6241342 6247792 6264307 6254220 6234611 6302528 6283582 6239821 6338547 6247796 6557977 6390603 6362843 6293653 6312107 6227653 6234609 6238040 6188415 6227654 6209989 6247791 6336710 6217153 6416167 6243113 6283581 6247790 6260953 6267469 6588882 6742873 6918655 6547371 6938989 6598964 6923526 6273544 6309048 6420196 6443558 6439689 6378989 6848181 6634735 6299289 6299290 6425654 6902255 6623101 6406129 6505916 6457809 6550895 6457812 7152962 6428133 7216956 7080895 11/144844 7182437 11/599341 11/635533 11/607976 11/607975 11/607999 11/607980 11/607979 11/607978 11/735961 11/685074 11/696126 11/696144 11/696650 11/763446 6224780 6235212 6280643 6284147 6214244 6071750 6267905 6251298 6258285 6225138 6241904 6299786 6866789 6231773 6190931 6248249 6290862 6241906 6565762 6241905 6451216 6231772 6274056 6290861 6248248 6306671 6331258 6110754 6294101 6416679 6264849 6254793 6245246 6855264 6235211 6491833 6264850 6258284 6312615 6228668 6180427 6171875 6267904 6245247 6315914 7169316 6526658 7210767 11/056146 11/635523 6665094 6450605 6512596 6654144 7125090 6687022 7072076 7092125 7215443 7136195 7077494 6877834 6969139 10/636227 7283280 6912067 7277205 7154637 10/636230 7070251 6851782 10/636211 10/636247 6843545 7079286 7064867 7065247 7027177 7218415 7064873 6954276 7061644 7092127 7059695 10/990382 7177052 7270394 11/124231 7188921 7187469 7196820 11/281445 7283281 7251051 7245399 11/524911 11/640267 11/706297 11/730387 11/737142 7336397 11/834637 11/853019 11/863239 12015485 12030797 11/305274 11/305273 11/305275 11/305152 11/305158 11/305008 6231148 6293658 6614560 6238033 6312070 6238111 6378970 6196739 6270182 6152619 7006143 6876394 6738096 6970186 6287028 6412993 11/033145 11/102845 11/102861 11/248421 11/672878 7204941 7282164 10/815628 11845672 7278727 10/913373 10/913374 10/913372 7138391 7153956 10/913380 10/913379 10/913376 7122076 7148345 11/172816 11/172815 11/172814 11/482990 11/482986 11/482985 11/454899 11/583942 11/592990 11849360 11/831961 11/831962 11/831963 60951700 11/832629 11/832637 60971535 61027756 10/407212 7252366 10/683064 10/683041 7275811 10/884889 10/922890 7334874 10/922885 10/922889 10/922884 10/922879 10/922887 10/922888 10/922874 7234795 10/922871 7328975 7293855 10/922882 10/922883 10/922878 10/922872 10/922876 10/922886 10/922877 7147792 7175774 11/159193 11/491378 11766713 11/841647 12018040 12035410 12037054 11/482980 11/563684 11/482967 11/482966 11/482988 11/482989 11/293832 11/293838 11/293825 11/293841 11/293799 11/293796 11/293797 11/293798 11/124158 11/124196 11/124199 11/124162 11/124202 11/124197 11/124154 11/124198 7284921 11/124151 11/124160 11/124192 11/124175 11/124163 11/124149 11/124152 11/124173 11/124155 7236271 11/124174 11/124194 11/124164 11/124200 11/124195 11/124166 11/124150 11/124172 11/124165 11/124186 11/124185 11/124184 11/124182 11/124201 11/124171 11/124181 11/124161 11/124156 11/124191 11/124159 11/124176 11/124188 11/124170 11/124187 11/124189 11/124190 11/124180 11/124193 11/124183 11/124178 11/124177 11/124148 11/124168 11/124167 11/124179 11/124169 11/187976 11/188011 11/188014 11/482979 11/735490 11/853018 11/944450 12023815 12035414 11/228540 11/228500 11/228501 11/228530 11/228490 11/228531 11/228504 11/228533 11/228502 11/228507 11/228482 11/228505 11/228497 11/228487 11/228529 11/228484 11/228489 11/228518 11/228536 11/228496 11/228488 11/228506 11/228516 11/228526 11/228539 11/228538 11/228524 11/228523 11/228519 11/228528 11/228527 11/228525 11/228520 11/228498 11/228511 11/228522 11/228515 11/228537 11/228534 11/228491 11/228499 11/228509 11/228492 11/228493 11/228510 11/228508 11/228512 11/228514 11/228494 11/228495 11/228486 11/228481 11/228477 11/228485 11/228483 11/228521 11/228517 11/228532 11/228513 11/228503 11/228480 11/228535 11/228478 11/228479 12035419 6238115 6386535 6398344 6612240 6752549 6805049 6971313 6899480 6860664 6925935 6966636 7024995 7284852 6926455 7056038 6869172 7021843 6988845 6964533 6981809 7284822 7258067 7322757 7222941 7284925 7278795 7249904 11/737726 11772240 11/863246 11/863145 11/865650 6087638 6340222 6041600 6299300 6067797 6286935 6044646 6382769 6787051 6938990 11/242916 11/144799 11/198235 11861282 11861284 11/766052 7152972 11/592996 D529952 6390605 6322195 6612110 6480089 6460778 6305788 6426014 6364453 6457795 6315399 6338548 7040736 6938992 6994425 6863379 6540319 6994421 6984019 7008043 6997544 6328431 6991310 10/965772 7140723 6328425 6982184 7267423 7134741 7066577 7152945 7303689 7021744 6991320 7155911 11/107799 6595624 7152943 7125103 7328971 7290857 7285437 7229151 11/330058 7237873 11/329163 11/442180 11/450431 7213907 6417757 11/482951 11/545566 11/583826 11/604315 11/604323 11/643845 11/706950 11/730399 11749121 11/753549 11/834630 11/935389 11/869670 7095309 11/945157 11957473 11967235 12017896 6854825 6623106 6672707 6575561 6817700 6588885 7075677 6428139 6575549 6846692 6425971 7063993 6383833 6955414 6412908 6746105 6953236 6412904 7128388 6398343 6652071 6793323 6659590 6676245 7201460 6464332 6659593 6478406 6978613 6439693 6502306 6966111 6863369 6428142 6874868 6390591 6799828 6896358 7018016 10/296534 6328417 6322194 6382779 6629745 6565193 6609786 6609787 6439908 6684503 6843551 6764166 6561617 10/510092 6557970 6546628 10/510098 6652074 6820968 7175260 6682174 7303262 6648453 6834932 6682176 6998062 6767077 7278717 6755509 10/534813 6692108 10/534811 6672709 7303263 7086718 10/534881 6672710 10/534812 6669334 7322686 7152958 7281782 6824246 7264336 6669333 10/534815 6820967 7306326 6736489 7264335 6719406 7222943 7188419 7168166 6974209 7086719 6974210 7195338 7252775 7101025 11/474281 11/485258 11/706304 11/706324 11/706326 11/706321 11/772239 11/782598 11/829941 11/852991 11852986 11/936062 11/934027 11955028 12034578 12036908 11/763440 11/763442 11/246687 11/246718 7322681 11/246686 11/246703 11/246691 11/246711 11/246690 11/246712 11/246717 11/246709 11/246700 11/246701 11/246702 11/246668 11/246697 11/246698 11/246699 11/246675 11/246674 11/246667 11/829957 11/829960 11/829961 11/829962 11/829963 11/829966 11/829967 11/829968 11/829969 11946839 11946838 11946837 11951230 7156508 7159972 7083271 7165834 7080894 7201469 7090336 7156489 10/760233 10/760246 7083257 7258422 7255423 7219980 10/760253 10/760255 10/760209 7118192 10/760194 7322672 7077505 7198354 7077504 10/760189 7198355 10/760232 7322676 7152959 7213906 7178901 7222938 7108353 7104629 11/446227 11/454904 11/472345 11/474273 7261401 11/474279 11/482939 7328972 7322673 7306324 7306325 11/603824 11/601756 11/601672 7303261 11/653253 11/706328 11/706299 11/706965 11/737080 11/737041 11/778062 11/778566 11/782593 11/934018 11/945157 11951095 11951828 11954906 11954949 11967226 7303930 11/246672 11/246673 11/246683 11/246682 60/939086 11860538 11860539 11/860540 11860541 11860542 11/936060 11877667 11877668 7246886 7128400 7108355 6991322 7287836 7118197 10/728784 10/728783 7077493 6962402 10/728803 7147308 10/728779 7118198 7168790 7172270 7229155 6830318 7195342 7175261 10/773183 7108356 7118202 10/773186 7134744 10/773185 7134743 7182439 7210768 10/773187 7134745 7156484 7118201 7111926 10/773184 7018021 11/060751 11/060805 11/188017 7128402 11/298774 11/329157 11/490041 11/501767 7284839 7246885 7229156 11/505846 11/505857 7293858 11/524908 11/524938 7258427 11/524912 7278716 11/592995 11/603825 11/649773 11/650549 11/653237 11/706378 11/706962 11749118 11/754937 11749120 11/744885 11/779850 11/765439 11/842950 11/839539 11/926121 12025621 11/097308 11/097309 7246876 11/097299 11/097310 11/097213 7328978 7334876 7147306 7261394 11/764806 11/782595 11965696 12/027286 11/482953 11/482977 11/544778 11/544779 11/764808 11/756624 11/756625 11/756626 11/756627 11/756628 11/756629 11/756630 11/756631 7156289 7178718 7225979 11/712434 11/084796 11/084742 11/084806 09/575197 09/575197 7079712 7079712 6825945 6825945 7330974 7330974 6813039 6813039 7190474 6987506 6987506 6824044 7038797 7038797 6980318 6980318 6816274 6816274 7102772 7102772 09/575186 09/575186 6681045 6681045 6678499 6679420 6963845 6976220 6728000 6728000 7110126 7173722 7173722 6976035 6813558 6766942 6965454 6995859 7088459 7088459 6720985 7286113 6922779 6978019 6847883 7131058 7295839 09/607843 09/693690 6959298 6973450 7150404 6965882 7233924 09/575181 09/575181 09/722174 7175079 7162259 6718061 10/291523 10/291471 7012710 6825956 10/291481 7222098 10/291825 7263508 7031010 6972864 6862105 7009738 6989911 6982807 10/291576 6829387 6714678 6644545 6609653 6651879 10/291555 7293240 10/291592 10/291542 7044363 7004390 6867880 7034953 6987581 7216224 10/291821 7162269 7162222 7290210 7293233 7293234 6850931 6865570 6847961 10/685523 10/685583 7162442 10/685584 7159784 10/804034 10/793933 6889896 10/831232 7174056 6996274 7162088 10/943874 10/943872 10/944044 7259884 10/944043 7167270 10/943877 6986459 10/954170 7181448 10/981626 10/981616 7324989 7231293 7174329 10/992713 7295922 7200591 11/020106 11/020260 11/020321 11/020319 11/026045 11/059696 11/051032 11/059674 11/107944 11/107941 11/082940 11/082815 11/082827 11/082829 6991153 6991154 11/124256 11/123136 11/154676 7322524 11/182002 11/202251 11/202252 11/202253 11/203200 11/202218 11/206778 11/203424 11/222977 7327485 11/227239 11/286334 7225402 11/329187 11/349143 11/491225 11/491121 11/442428 11/454902 11/442385 11/478590 7271931 11/520170 11/603057 11/706964 11/739032 11739014 7336389 11/830848 11/830849 11/839542 11/866394 11/934077 11951874 12015487 12023860 12023005 12036266 7068382 7068382 7007851 6957921 6457883 10/743671 7044381 11/203205 7094910 7091344 7122685 7038066 7099019 7062651 7062651 6789194 6789194 6789191 6789191 10/900129 7278018 10/913350 10/982975 10/983029 11/331109 6644642 6644642 6502614 6502614 6622999 6622999 6669385 6669385 6827116 7011128 10/949307 6549935 6549935 6987573 6987573 6727996 6727996 6591884 6591884 6439706 6439706 6760119 6760119 7295332 7295332 7064851 6826547 6290349 6290349 6428155 6428155 6785016 6785016 6831682 6741871 6927871 6980306 6965439 6840606 7036918 6977746 6970264 7068389 7093991 7190491 10/901154 10/932044 10/962412 7177054 10/962552 10/965733 10/965933 10/974742 10/982974 7180609 10/986375 11/107817 7292363 11/149160 11/206756 11/250465 7202959 11/653219 11/706309 11/730389 11/730392 60/953443 11/866387 60974077 6982798 6870966 6870966 6822639 6822639 6474888 6627870 6724374 6788982 7263270 6788293 6946672 6737591 6737591 7091960 09/693514 6792165 7105753 6795593 6980704 6768821 7132612 7041916 6797895 7015901 7289882 7148644 10/778056 10/778058 10/778060 10/778059 10/778063 10/778062 10/778061 10/778057 7096199 7286887 10/917467 10/917466 7324859 7218978 7245294 7277085 7187370 10/917436 10/943856 10/919379 7019319 10/943878 10/943849 7043096 7148499 11/144840 11/155556 11/155557 11/193481 11/193435 11/193482 11/193479 7336267 11/281671 11/298474 7245760 11/488832 11/495814 11/495823 11/495822 11/495821 11/495820 11/653242 11/754370 60911260 11/829936 11/839494 11866305 11866313 11866324 11866336 11866348 11866359 11970951 12036264 7055739 7055739 7233320 7233320 6830196 6830196 6832717 6832717 7182247 7120853 7082562 6843420 10/291718 6789731 7057608 6766944 6766945 7289103 10/291559 7299969 7264173 10/409864 7108192 10/537159 7111791 7077333 6983878 10/786631 7134598 10/893372 6929186 6994264 7017826 7014123 7134601 7150396 10/971146 7017823 7025276 7284701 7080780 11/074802 7334739 11749158 11/842948 12015477 12025746 12025747 12025748 12025749 12025750 12025751 12025754 12025756 12025757 12025759 12025760 12025761 12025762 12025764 12025765 12025766 12025767 12025768 10/492169 10/492152 10/492168 10/492161 7308148 10/502575 10/531229 10/683151 10/531733 10/683040 10/510391 10/919260 10/510392 10/778090 11/944404 11/936638 12031615 6957768 6957768 09/575172 09/575172 7170499 7170499 7106888 7106888 7123239 7123239 6982701 6982703 7227527 6786397 6947027 6975299 7139431 7048178 7118025 6839053 7015900 7010147 7133557 6914593 10/291546 6938826 7278566 7123245 6992662 7190346 11/074800 11/074782 11/074777 11/075917 7221781 11/102843 7213756 11/188016 7180507 7263225 7287688 11/737094 11/753570 11/782596 11/865711 12036904 11856061 11856062 11856064 11856066 11/672522 11/672950 11/672947 11/672891 11/672954 11/672533 11754310 11/754321 11/754320 11/754319 11/754318 11/754317 11/754316 11/754315 11/754314 11/754313 11/754312 11/754311 12015507 12015508 12015509 12015510 12015511 12015512 12015513 6593166 7132679 6940088 7119357 7307272 6755513 6974204 6409323 7055930 6281912 6893109 6604810 6824242 6318920 7210867 6488422 6655786 6457810 6485135 6796731 6904678 6641253 7125106 6786658 7097273 6824245 7222947 6918649 6860581 6929351 7063404 6969150 7004652 6871938 6905194 6846059 6997626 7303256 7029098 6966625 7114794 7207646 7077496 7284831 11/072529 7152938 7182434 7182430 7306317 7032993 7325905 11/155545 11/144813 7172266 7258430 7128392 7210866 7306322 11/505933 11/540727 11/635480 11/707946 11/706303 11/709084 11/730776 11/744143 11/779845 11/782589 11/863256 11/940302 11/940235 11955359 12019583 12019566 12036910 11/066161 11/066160 11/066159 11/066158 7287831 11/875936 12017818 6804030 6807315 6771811 6683996 7271936 7304771 6965691 7058219 7289681 7187807 7181063 11/338783 11/603823 11/650536 12025633 10/727181 10/727162 10/727163 10/727245 7121639 7165824 7152942 10/727157 7181572 7096137 7302592 7278034 7188282 10/727159 10/727180 10/727179 10/727192 10/727274 10/727164 10/727161 10/727198 10/727158 10/754536 10/754938 10/727227 10/727160 10/934720 7171323 7278697 11/442131 11/474278 11/488853 7328115 11749750 11749749 11955127 11951213 10/296522 6795215 7070098 7154638 6805419 6859289 6977751 6398332 6394573 6622923 6747760 6921144 10/884881 7092112 7192106 11/039866 7173739 6986560 7008033 11/148237 7222780 7270391 7150510 11/478599 11/499749 11/521388 11/738518 11/482981 11/743662 11/743661 11/743659 11/743655 11/743657 11/752900 11926109 11/927163 11929567 7195328 7182422 11/650537 11/712540 10/854521 10/854522 10/854488 7281330 10/854503 10/854504 10/854509 7188928 7093989 10/854497 10/854495 10/854498 10/854511 10/854512 10/854525 10/854526 10/854516 7252353 10/854515 7267417 10/854505 10/854493 7275805 7314261 10/854490 7281777 7290852 10/854528 10/854523 10/854527 10/854524 10/854520 10/854514 10/854519 10/854513 10/854499 10/854501 7266661 7243193 10/854518 10/854517 10/934628 7163345 7322666 11/601757 11/706295 11/735881 11748483 11749123 11/766061 11775135 11772235 11/778569 11/829942 11/870342 11/935274 11/937239 11961907 11961940 11961961 11/014731 D529081 D541848 D528597 6924907 6712452 6416160 6238043 6958826 6812972 6553459 6967741 6956669 6903766 6804026 7259889 6975429 10/636234 10/636233 7301567 10/636216 7274485 7139084 7173735 7068394 7286182 7086644 7250977 7146281 7023567 7136183 7083254 6796651 7061643 7057758 6894810 6995871 7085010 7092126 7123382 7061650 10/853143 6986573 6974212 7307756 7173737 10/954168 7246868 11/065357 7137699 11/107798 7148994 7077497 11/176372 7248376 11/225158 7306321 7173729 11/442132 11/478607 11/503085 11/545502 11/583943 11/585946 11/653239 11/653238 11/764781 11/764782 11/779884 11845666 11/872637 11/944401 11/940215 11/544764 11/544765 11/544772 11/544773 11/544774 11/544775 11/544776 11/544766 11/544767 11/544771 11/544770 11/544769 11/544777 11/544768 11/544763 11/293804 11/293840 11/293803 11/293833 11/293834 11/293835 11/293836 11/293837 11/293792 11/293794 11/293839 11/293826 11/293829 11/293830 11/293827 11/293828 7270494 11/293823 11/293824 11/293831 11/293815 11/293819 11/293818 11/293817 11/293816 11/838875 11/482978 11/640356 11/640357 11/640358 11/640359 11/640360 11/640355 11/679786 11/872714 10/760254 10/760210 10/760202 7201468 10/760198 10/760249 7234802 7303255 7287846 7156511 10/760264 7258432 7097291 10/760222 10/760248 7083273 10/760192 10/760203 10/760204 10/760205 10/760206 10/760267 10/760270 7198352 10/760271 7303251 7201470 7121655 7293861 7232208 7328985 10/760261 7083272 7261400 11/474272 11/474315 7311387 11/583874 7303258 11/706322 11/706968 11/749119 11749157 11779848 11/782590 11/855152 11855151 11/870327 11/934780 11/935992 11951193 12/017327 12015273 12036882 11/014764 11/014763 7331663 11/014747 7328973 11/014760 11/014757 7303252 7249822 11/014762 7311382 11/014723 11/014756 11/014736 11/014759 11/014758 11/014725 7331660 11/014738 11/014737 7322684 7322685 7311381 7270405 7303268 11/014735 11/014734 11/014719 11/014750 11/014749 7249833 11/758640 11/775143 11/838877 11944453 11/944633 11955065 12/003952 12007818 12007817 12071187 11/014769 11/014729 7331661 11/014733 7300140 11/014755 11/014765 11/014766 11/014740 7284816 7284845 7255430 11/014744 7328984 11/014768 7322671 11/014718 11/014717 11/014716 11/014732 11/014742 11/097268 11/097185 11/097184 11/778567 11852958 11852907 11/872038 11955093 11961578 12022023 12023000 12023018 12031582 12043708 11/293820 11/293813 11/293822 11/293812 11/293821 11/293814 11/293793 11/293842 11/293811 11/293807 11/293806 11/293805 11/293810 11/688863 11/688864 11/688865 11/688866 11/688867 11/688868 11/688869 11/688871 11/688872 11/688873 11/741766 12014767 12014768 12014769 12014770 12014771 12014772 12014773 12014774 12014775 12014776 12014777 12014778 12014779 12014780 12014781 12014782 12014783 12014784 12014785 12014787 12014788 12014789 12014790 12014791 12014792 12014793 12014794 12014796 12014798 12014801 12014803 12014804 12014805 12014806 12014807 61034147 11/482982 11/482983 11/482984 11/495818 11/495819 11/677049 11/677050 11/677051 11872719 11872718 61033357 7306320 11/934781 D528156 10/760180 7111935 10/760213 10/760219 10/760237 7261482 10/760220 7002664 10/760252 10/760265 7088420 11/446233 11/503083 11/503081 11/516487 11/599312 6364451 6533390 6454378 7224478 6559969 6896362 7057760 6982799 11/202107 11/743672 11744126 11/743673 7093494 7143652 7089797 7159467 7234357 7124643 7121145 7089790 7194901 6968744 7089798 7240560 7137302 11/442177 7171855 7260995 7260993 7165460 7222538 7258019 11/543047 7258020 11/604324 7334480 11/706305 11/707056 11744211 11/767526 11/779846 11/764227 11/829943 11/829944 12015390 12031475 6454482 6808330 6527365 6474773 6550997 7093923 6957923 7131724 10/949288 7168867 7125098 11/706966 11/185722 7249901 7188930 11/014728 11/014727 D536031 D531214 7237888 7168654 7201272 6991098 7217051 6944970 10/760215 7108434 10/760257 7210407 7186042 10/760266 6920704 7217049 10/760214 10/760260 7147102 7287828 7249838 10/760241 10/962413 10/962427 7261477 7225739 10/962402 10/962425 10/962428 7191978 10/962426 10/962409 10/962417 10/962403 7163287 7258415 7322677 7258424 10/962410 7195412 7207670 7270401 7220072 11/474267 11/544547 11/585925 11/593000 11/706298 11/706296 11/706327 11/730760 11/730407 11/730787 11/735977 11/736527 11/753566 11/754359 11/778061 11/765398 11/778556 11/829937 11/780470 11/866399 11/223262 11/223018 11/223114 11955366 7322761 11/223021 11/223020 11/223019 11/014730 D541849 29/279123 6716666 6949217 6750083 7014451 6777259 6923524 6557978 6991207 6766998 6967354 6759723 6870259 10/853270 6925875 10/898214 7095109 7145696 10/976081 7193482 7134739 7222939 7164501 7118186 7201523 7226159 7249839 7108343 7154626 7079292 10/980184 7233421 7063408 10/983082 10/982804 7032996 10/982834 10/982833 10/982817 7217046 6948870 7195336 7070257 10/986813 10/986785 7093922 6988789 10/986788 7246871 10/992748 10/992747 7187468 10/992828 7196814 10/992754 7268911 7265869 7128384 7164505 7284805 7025434 7298519 7280244 7206098 7265877 7193743 7168777 11/006734 7195329 7198346 7281786 11/013363 11/013881 6959983 7128386 7097104 11/013636 7083261 7070258 7083275 7110139 6994419 6935725 11/026046 7178892 7219429 6988784 11/026135 7289156 11/064005 7284976 7178903 7273274 7083256 7325986 7278707 7325918 6974206 11/064004 7066588 7222940 11/075918 7018025 7221867 7290863 7188938 7021742 7083262 7192119 11/083021 7036912 7175256 7182441 7083258 7114796 7147302 11/084757 7219982 7118195 7229153 6991318 7108346 11/248429 11/239031 7178899 7066579 11/281419 20060087544 11/329188 11/329140 7270397 7258425 7237874 7152961 7333235 7207658 11/484744 7311257 7207659 11/525857 11/540569 11/583869 11/592985 11/585947 7306307 11/604316 11/604309 11/604303 11/643844 7329061 11/655940 11/653320 7278713 11/706381 11/706323 11/706963 11/713660 7290853 11/696186 11/730390 11/737139 11/737749 11/740273 11749122 11/754361 11766043 11/764775 11/768872 11/775156 11/779271 11/779272 11/829938 11/839502 11858852 11/862188 11859790 11/872618 11/923651 11950255 11930001 11955362 12015368 11965718 6485123 6425657 6488358 7021746 6712986 6981757 6505912 6439694 6364461 6378990 6425658 6488361 6814429 6471336 6457813 6540331 6454396 6464325 6443559 6435664 6412914 6488360 6550896 6439695 6447100 09/900160 6488359 6637873 10/485738 6618117 10/485737 6803989 7234801 7044589 7163273 6416154 6547364 10/485744 6644771 7152939 6565181 7325897 6857719 7255414 6702417 7284843 6918654 7070265 6616271 6652078 6503408 6607263 7111924 6623108 6698867 6488362 6625874 6921153 7198356 6536874 6425651 6435667 10/509997 6527374 7334873 6582059 10/510152 6513908 7246883 6540332 6547368 7070256 6508546 10/510151 6679584 7303254 6857724 10/509998 6652052 10/509999 6672706 10/510096 6688719 6712924 6588886 7077508 7207654 6935724 6927786 6988787 6899415 6672708 6644767 6874866 6830316 6994420 6954254 7086720 7240992 7267424 7128397 7084951 7156496 7066578 7101023 11/165027 11/202235 11/225157 7159965 7255424 11/349519 7137686 7201472 7287829 11/504602 7216957 11/520572 11/583858 11/583895 11/585976 11/635488 7278712 11/706952 11/706307 7287827 11944451 11/740287 11/754367 11/758643 11/778572 11859791 11/863260 11/874178 11/936064 11951983 12015483 6916082 6786570 10/753478 6848780 6966633 7179395 6969153 6979075 7132056 6832828 6860590 6905620 6786574 6824252 7097282 6997545 6971734 6918652 6978990 6863105 10/780624 7194629 10/791792 6890059 6988785 6830315 7246881 7125102 7028474 7066575 6986202 7044584 7210762 7032992 7140720 7207656 7285170 11/048748 7008041 7011390 7048868 7014785 7131717 7284826 7331101 7182436 7104631 7240993 7290859 11/202217 7172265 7284837 7066573 11/298635 7152949 7334877 11/442133 7326357 7156492 11/478588 7331653 7287834 11/525861 11/583939 11/545504 7284326 11/635485 11/730391 11/730788 11/749148 11/749149 11/749152 11/749151 11/759886 11/865668 11/874168 11/874203 11971182 12021086 12015441 11965722 6824257 7270475 6971811 6878564 6921145 6890052 7021747 6929345 6811242 6916087 6905195 6899416 6883906 6955428 7284834 6932459 6962410 7033008 6962409 7013641 7204580 7032997 6998278 7004563 6910755 6969142 6938994 7188935 10/959049 7134740 6997537 7004567 6916091 7077588 6918707 6923583 6953295 6921221 7001008 7168167 7210759 7337532 7331659 7322680 6988790 7192120 7168789 7004577 7052120 11/123007 6994426 7258418 7014298 7328977 11/177394 7152955 7097292 7207657 7152944 7147303 7338147 7134608 7264333 7093921 7077590 7147297 20060038853 11/248832 11/248428 11/248434 7077507 7172672 7175776 7086717 7101020 11/329155 7201466 11/330057 7152967 7182431 7210666 7252367 7287837 11/485255 11/525860 6945630 7018294 6910014 6659447 6648321 7082980 6672584 7073551 6830395 7289727 7001011 6880922 6886915 6644787 6641255 7066580 6652082 7284833 6666544 6666543 6669332 6984023 6733104 6644793 6723575 6953235 6663225 7076872 7059706 7185971 7090335 6854827 6793974 10/636258 7222929 6739701 7073881 7155823 7219427 7008503 6783216 6883890 6857726 10/636274 6641256 6808253 6827428 6802587 6997534 6959982 6959981 6886917 6969473 6827425 7007859 6802594 6792754 6860107 6786043 6863378 7052114 7001007 10/729151 10/729157 6948794 6805435 6733116 10/683006 7008046 6880918 7066574 6983595 6923527 7275800 7163276 7156495 6976751 6994430 7014296 7059704 7160743 7175775 7287839 7097283 7140722 11/123009 11/123008 7080893 7093920 7270492 7128093 7052113 7055934 11/155627 7278796 11/159197 7083263 7145592 7025436 11/281444 7258421 11/478591 7332051 7226147 11/482940 7195339 11/503061 11/505938 7284838 7293856 11/544577 11/540576 7325901 11/592991 11/599342 11/600803 11/604321 11/604302 11/635535 11/635486 11/643842 11/655987 11/650541 11/706301 11/707039 11/730388 11/730786 11/730785 11/739080 7322679 11/768875 11/779847 11/829940 11847240 11/834625 11/863210 11/865680 11/874156 11/923602 11951940 11954988 11961662 12015178 12015157 12/017305 12017926 12015261 12025605 12031646 7067067 6776476 6880914 7086709 6783217 7147791 6929352 7144095 6820974 6918647 6984016 7192125 6824251 6834939 6840600 6786573 7144519 6799835 6959975 6959974 7021740 6935718 6938983 6938991 7226145 7140719 6988788 7022250 6929350 7011393 7004566 7175097 6948799 7143944 7310157 7029100 6957811 7073724 7055933 7077490 7055940 10/991402 7234645 7032999 7066576 7229150 7086728 7246879 7284825 7140718 7284817 7144098 7044577 7284824 7284827 7189334 7055935 7152860 11/203188 11/203173 7334868 7213989 11/225156 11/225173 7300141 7114868 7168796 7159967 7328966 7152805 11/298530 11/330061 7133799 11/330054 11/329284 7152956 7128399 7147305 7287702 7325904 7246884 7152960 11/442125 11/454901 11/442134 11/450441 11/474274 11/499741 7270399 6857728 6857729 6857730 6989292 7126216 6977189 6982189 7173332 7026176 6979599 6812062 6886751 10/804057 10/804036 7001793 6866369 6946743 7322675 6886918 7059720 7306305 10/846562 7334855 10/846649 10/846627 6951390 6981765 6789881 6802592 7029097 6799836 7048352 7182267 7025279 6857571 6817539 6830198 6992791 7038809 6980323 7148992 7139091 6947173 7101034 6969144 6942319 6827427 6984021 6984022 6869167 6918542 7007852 6899420 6918665 6997625 6988840 6984080 6845978 6848687 6840512 6863365 7204582 6921150 7128396 6913347 7008819 6935736 6991317 7284836 7055947 7093928 7100834 7270396 7187086 7290856 7032825 7086721 7159968 7010456 7147307 7111925 11/144812 7229154 11/505849 11/520570 7328994 7341672 11/540575 11/583937 7278711 7290720 7314266 11/635489 11/604319 11/635490 11/635525 7287706 11/706366 11/706310 11/706308 11/785108 11/744214 11744218 11748485 11/748490 11/764778 11/766025 11/834635 11839541 11860420 11/865693 11/863118 11/866307 11/866340 11/869684 11/869722 11/869694 11/876592 11/945244 11951121 11/945238 11955358 11965710 11962050 12015478 12015423 12015434 12023015 12030755 12025641 12036279 12031598

BACKGROUND OF THE INVENTION

An integrated circuit fabricated on the silicon wafer is often referred to as a ‘die’. For the purposes of this specification, the term die will be used as a reference to an integrated circuit fabricated on a wafer substrate using lithographic the well known etching and deposition techniques commonly used in semiconductor fabrication. Integrated circuit (IC) dies are electrically connected to printed circuit boards by wire bonds. The wire bonds are very thin wires—around 25 to 40 microns in diameter—extending from contact pads along the side of the wafer substrate to contacts on the printed circuit board (PCB). Wire bonding is a widely used electrical interconnection technique because of the speed and accuracy of modern wire bonding machines, commonly referred to as wire bonders.

Wire bonders are automated devices that weld small lengths of wire from conductors on the PCB to the contact pads on an integrated circuit die. Wire is fed through a bonding tool that uses some combination of pressure, heat and/or ultra-sonic energy to attach the wire to the bond pads via a solid phase welding process. The two most common types of wire bonder are referred to as wedge bond and ball bond. These refer to the bonding tool and the configuration of the wire bond itself. With both types of wire bonders, the individual wire bonds extend in an arc from the bond pad on the integrated circuit (IC) die to the conductor on the PCB. This is because wires from the contact pads to the PCB are made longer than necessary to accommodate changes in the gap between the PCB and the bonds pads due to thermal expansion, flex in the components and so on.

To protect and strengthen the wire bonds, they are sealed within a bead of epoxy called encapsulant. The top of the wire arc is often about 300 microns above the contact pads although some wire bonding may extend even higher. As the name suggests, the encapsulant needs to encapsulate the full length of the wire so the encapsulant bead will extend 500 microns to 600 microns proud of the contact pads.

If the die is purely an electronic microprocessor, there is little need to keep close control of the encapsulant bead dimensions. However, if the die is a micro-electro mechanical systems (MEMS) device with an active upper surface, it may be necessary or desirable to bring the active surface of the die onto close proximity with another surface. One such situation applies to inkjet print heads. The proximity of the print media to the nozzle array influences the print quality. Similarly, if a cleaning surface is wiped across the nozzles, the bead of encapsulant can hamper the wiping contact.

Another problems arises because of sides of the encapsulant bead are not straight. One commonly used technique for depositing the encapsulant involves extruding it from a needle directly onto the line of wire bonds. The encapsulant volume and placement on the die is not very accurate. Variations in the pressure from the pump or slight non-uniformities in the speed of the needle cause the side of the bead contacting the active surface to be reasonably crooked. As the side of the bead is not straight, it has to be generously spaced from any active parts on the active surface to comfortably accommodate the perturbations. Spacing the electrical contacts away from the active portions (say for example, inkjet nozzles) of the active surface uses up valuable wafer real estate and reduces the number of dies that can be fabricated from a wafer disc.

In light of the widespread use of inkjet print heads, the invention will be described with specific reference to its application in this field. However, the ordinary worker will appreciate that this is purely illustrative and the invention is equally applicable to other integrated circuits wire bonded to a PCB or other support structure.

SUMMARY OF THE INVENTION

According to a first aspect, the present invention provides a method of profiling a series of wire bonds between a line of contact pads on a die, and a corresponding set of conductors on a supporting structure, the method comprising the steps of:

electrically connecting each of the contact pads on the die to a corresponding conductor on the supporting structure with a respective wire bond, each of the wire bonds extending in an arc from the contact pad to the conductor; and,

pushing on each of the wire bonds individually to collapse the arc and plastically deform the wire bond such that the plastic deformation maintains the wire bond in a flatter profile shape.

The strength of the wire bond is known to be relatively small; of the order of 3 to 5 grams force. However, the Applicant's work has found that the wire bond structure is robust enough to withstand a certain degree of work hardening from plastic deformation. The arc of the wire bond can be deformed into a flatter profile without compromising the electrical connection with the PCB. The Applicant's above referenced U.S. Ser. No. 11/860,539 (Our Docket MPN008US) discloses a technique for simultaneously pushing some or all of the wire loops in the line of wire bonds. This so called gang wire pushing technique is effective but further development has shown that individually collapsing each wire bond is more controlled and easier to implement in a high volume manufacturing process.

Preferably, adjacent wire bonds in the line of wire bonds are sequentially pushed. In a further preferred form, the step of forming the line of wire bonds uses a wire bonder that has a bonding tool for moving between the contacts pads and their respective corresponding conductors, and the line of wires bonds are sequentially pushed by a wire engaging structure on the wire bonder. Preferably, the wire engaging structure and the bonding tools are configured for synchronized movement. Preferably, the wire engaging structure pushes the wire bond immediately adjacent the wire bond currently being formed by the bonding tool. Preferably, the wire bonder is a wedge type wire bonder and the bonding tool is a wedge with a wire clamp at a distal end such that during use, the wire clamp holds a piece of wire in contact with one of the contact pads on the die to form a weld connection before moving to the corresponding conductor on the PCB to weld the other end of the wire and formal wire bond, and the wire engaging structure has a wire pushing surface that contacts the wire bond, the wire pushing surface is adjacent to, and 1.0 mm to 1.6 mm behind the wire clamp with respect to the movement of the wedge towards the IC die. In a particularly preferred form, the wire pushing surface is between 50 microns to 400 microns closer to the PCB and the wire clamp. In some embodiments, the line of wire bonds does not extend more than 150 microns above the contact pads of the IC die. In preferred embodiments, the line of wire bonds does not extend more than 50 microns above the contact pads of the IC die. In a particularly preferred form, the wire bonds are attached to the contact pads with a bond strength greater than 3 g force.

Preferably the contact pads are spaced from the corresponding conductors on the PCB by more than 1 mm. In a further preferred form, the contact pads are between 2 mm and 3 mm from the corresponding conductors on the PCB. In some embodiments, the PCB has a support structure and the flex PCB and need to the support structure such that the conductors are adjacent the contact pads on the die. In particular embodiments, the support structure has a chip mounting area for supporting the die, the die having a back surface in contact with the chip mounting area and an active surface opposing the back surface, the active surface having the contact pads, and the chip mounting area being raised relative to the remainder of the support structure such that the contact pads are raised relative to the conductors. In a particularly preferred form, the support structure is a liquid crystal polymer (LCP) molding. Preferably, the active surface has functional elements spaced less than 260 microns from the contacts pads of the die. In a particularly preferred form, the die is an inkjet print head IC and the functional elements are nozzles through which ink is ejected. In some embodiments, the support structure is a liquid crystal polymer (LCP) molding.

Preferably, the wire bonds are covered in a bead of encapsulant, the bead of encapsulant extending less than 200 microns above the active surface of the die.

Preferably, the wire bonds are covered in a bead of encapsulant, the bead of encapsulant having a profiled surface that is flat, parallel to and spaced less than 100 microns from the active surface.

Preferably, the line of wire bonds are covered in a bead of encapsulant, the bead of encapsulant having a profiled surface that is flat and inclined relative to the active surface.

Preferably, the wire bonds are covered in a bead of encapsulant, the encapsulant being an epoxy material that is thixotropic when uncured.

Preferably, the wire bonds are covered in a bead of encapsulant, the encapsulant being an epoxy material has a viscosity greater than 700 cp when uncured.

In a particular embodiment, the print head IC is mounted in a printer such that during use the nozzles are less than 100 microns from the paper path.

According to a second aspect, the present invention provides a wire bonder for electrically connecting an integrated circuit die with conductors on a printed circuit board, the wire bonder comprising:

a bonding tool for attaching wire bonds from the integrated circuit die to the conductors of the printed circuit board; and,

a wire engaging structure for deforming the wire bonds.

Preferably, the wire engaging structure pushes on the wire bonds to plastically deform them.

Preferably, the wire engaging structure is configured to push the wire bonds onto an adhesive surface positioned between the integrated circuit and the conductors of the printed circuit board.

Preferably, the wire engaging structure is flexible relative to the bonding tool.

Preferably, the wire engaging structure is configured for synchronized movement with the bonding tool.

Preferably, the bonding tool moves from the integrated circuit to the conductors when forming one of the wire bonds and the wire engaging structure has a wire pushing surface positioned 1.0 mm to 1.6 mm behind the bonding tool with respect to its direction of movement when forming the wire bonds.

Preferably, the integrated circuit die is mounted to a supporting surface and the wire pushing surface is 50 microns to 400 microns closer to the supporting surface than the bonding tool. Preferably, the wire bonder is a wedge type wire bonder and the bonding tool is a wedge with a wire clamp at a distal end such that during use, the wire clamp holds a piece of wire in contact with one of the contact pads on the die to form a weld connection before moving to the corresponding conductor on the PCB to weld the other end of the wire and formal wire bond. Preferably, the wire pushing surface is formed from a material that has a hardness less than that of the wire bonds.

Preferably, the wire bonds are formed from lengths of wire with a gauge between 15 microns and 75 microns. In a particularly preferred form, the gauge is about 25 microns.

In some embodiments, the wire bonds attach to respective contact pads on the IC die and the wire bonds do not extend more than 150 microns above the contact pads of the IC die. In preferred embodiments, the line of wire bonds does not extend more than 50 microns above the contact pads of the IC die.

Preferably the contact pads are spaced from the corresponding conductors on the PCB by more than 1 mm. In a further preferred form, the contact pads are between 2 mm and 3 mm from the corresponding conductors on the PCB. In some embodiments, the PCB has a support structure and the flex PCB and need to the support structure such that the conductors are adjacent the contact pads on the die. In particular embodiments, the support structure has a chip mounting area for supporting the die, the die having a back surface in contact with the chip mounting area and an active surface opposing the back surface, the active surface having the contact pads, and the chip mounting area being raised relative to the remainder of the support structure such that the contact pads are raised relative to the conductors. In a particularly preferred form, the support structure is a liquid crystal polymer (LCP) molding. Preferably, the active surface has functional elements spaced less than 260 microns from the contacts pads of the die. In a particularly preferred form, the die is an inkjet print head IC and the functional elements are nozzles through which ink is ejected. In some embodiments, the support structure is a liquid crystal polymer (LCP) molding.

According to a third aspect, the present invention provides an electronic device comprising:

an integrated circuit die with a plurality of contacts pads;

a printed circuit board with a plurality of conductors corresponding to each of the contact pads respectively;

wire bonds electrically connecting each of the contact pads to the corresponding conductors; and,

an adhesive surface positioned between the contacts pads and the corresponding conductors; wherein,

the wire bonds are secured to the adhesive surface.

According to a fourth aspect, the present invention provides a method of reducing wire bond loop heights in wire bonds electrically connecting an integrated circuit die with a contact pad to a printed circuit board with a conductor, the method comprising the steps of:

mounting the integrated circuit die such that the contact pad is spaced from the conductor;

positioning an adhesive surface between the contact pad and the conductor on the printed circuit board;

attaching wire to one of the contact pad or the conductor;

drawing the wire towards the other of the contact pad or the conductor;

allowing the wire to contact the adhesive surface; and,

attaching the wire to the other of the contact pad of the conductor to form a wire bond adhered to the adhesive surface and a point intermediate its ends.

These aspects of the invention are placed on the realization that wire bonds can be adhered to an underlying supporting structure without detrimental effects to their bond strength or function. Adhering the wire bonds between their ends provides a reliable and control production in the wire bond loop height. The resulting wire bond heights can be smaller than that achieved by inducing plastic deformation as the individual wire is unable to spring back up when the wire engaging structure disengages. It will be appreciated that plastically deforming a wire bond also involves initially elastically deforming the wire. The elastic deformation is removed when the wire pushing structure is retracted.

The wire bond can be adhered while the bonds are being formed by the wire bonder without any modification to the bonding tool. The applicant has found that wire bond is will typically allow the wire to touch the surface between the die and the conductors on the printed circuit board as the bond is being formed. Once the wire has been welded to the contact pad on the die, the bonding tool draws is towards the conductors on the printed circuit board. As it is drawn across the gap between the die and printed circuit board, the wire drapes downwardly and rests on the underlying surface. The only once the bonding tool has welded the other end of the wire to the conductor, and the wire clamp immediately behind the bonding tool breaks off the feed wire by pulling until tensile failure, does residual tension in the loop cause it to bow upwards. If the wire is brought down to touch an adhesive surface before the ultrasonic weld on the printed circuit board, it is not able to bow upwards.

Preferably, the wire bond is moved into contact with the adhesive surface by a wire bonder is the wire bond is being formed.

Preferably, the adhesive surface is one side of a double-sided adhesive tape. Preferably, the integrated circuit die and the PCB are mounted to a supporting structure such that they are adjacent and spaced from each other. Preferably, the PCB is a flexible PCB and the supporting structure is a liquid crystal polymer (LCP) molding. Preferably, the integrated circuit die is mounted to the supporting structure by a die attach film, and the adhesive surface is provided by a portion of the die attach film.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of a common prior art technique for applying a bead of encapsulant to wire bonds;

FIG. 2 is a schematic representation of a die mounted to a supporting structure with a chip mounting area raised relative to the flex PCB mounting area;

FIGS. 3A, 3B and 3C are schematic representations of the encapsulant bead being profiled into a desired shape using a moveable blade;

FIGS. 4A to 4D are schematic representations of wire bonds being profiled by plastic deformation;

FIGS. 5A and 5B show the encapsulant bead height reductions for plastically deformed wire bonds;

FIGS. 6A to 6C show the encapsulant bead being applied to the wire bonds using the profiling blade;

FIGS. 7A and 7B show the profiling blade being used to control the encapsulant bead front on the surface of the die;

FIG. 8 shows the wire pusher mounted to the wire bonder;

FIG. 9 shows the wire pusher and the wire bonder in profile; and,

FIG. 10 shows the wire bonds adhered to the LCP molding between the die and the flex PCB.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows a common technique used for applying a bead encapsulant to wire bonds. A die 4 is mounted to a supporting structure 6 adjacent the edge of a flex PCB 8 (flexible printed circuit board). The die 4 has a line of contact pads 10 along one edge and the flex PCB 8 has corresponding bond pads 12. Wire bonds 16 extend from the bond pads 10 to the bonds pads 12. Power and data is transmitted to the die 4 via conductive traces 14 in the flex PCB 8. This is a simplified representation of the dies mounted within many electronic devices. The print head IC dies mounted to the LCP (liquid crystal polymer) molding to receive print data from an adjacent flex PCB, as described in U.S. Ser. No. 11/014769 (Docket No. RRC001US) incorporated herein by cross reference, is one example of this type of die mounting arrangement. The ordinary worker will appreciate that the die may also be mounted directly to a hard PCB with traces formed thereon.

The wire bonds 16 are covered in a bead on encapsulant 2 to protect and reinforce the bonds. The encapsulant 2 is dispensed from a discharge needle 18 directly onto the wire bonds 16. Often the encapsulant bead 2 is three separate beads—two beads of so-called ‘dam’ encapsulant 20, and one bead of ‘fill’ encapsulant 22. The dam encapsulant 20 has a higher viscosity than the fill encapsulant 22, and serves to form a channel to hold the fill encapsulant bead. The height H of the bead 2 above the die 4 is usually about 500-600 microns. In most electronic devices, this does not pose a problem. However, if the die has an active surface that needs to operate in close proximity to another surface, this bead can be an obstruction.

Elevating the Die Relative to the Flex PCB

FIG. 2 shows a stepped support structure 6 that has raised the chip mounting area 26 relative to the PCB mounting area 24 (or at least the area mounting the PCB bonds pads 12). With the die 4 on a raised chip mounting area 26, the arc of the wire bonds 16 are lower relative to active surface 28 of the die 4. In fact, the end of the wire bond 16 attached to the contact pad 10 can be the apex of the arc (bearing in mind that the wire bond arc is intended to accommodate some relative movement of the die and PCB). When the wire bonds 16 are covered with encapsulant 2, the bead has a reduced height H above the active surface 28 of the die 4. If the bead of encapsulant 2 uses two beads of dam encapsulant 24 and a fill encapsulant 22, the positions, volumes and viscosities of the beads need to take the step into account. Bead heights less than 100 microns are easily achievable, and with additional measures, such as wire arc collapsing and bead profiling (discussed below), bead height of less than 50 microns are possible.

With the die 4 raised above the flex PCB 8 by 410 microns, the height of the wire bonds 16 above the die is about 34 microns. With the die raised 610 microns above the flex PCB, the wire bond height is around 20 microns. Raising the die even further has shown little or no further reduction in wire bond height with a step of 710 microns having a wire bond height of around 20 microns.

Shaping the Encapsulant Bead with a Profiling Blade

FIGS. 3A to 3C show the encapsulant 2 being profiled with a profiling blade 30. The support structure 6 is again stepped to reduce the height of the wire bonds 16 above the die 4. Before the epoxy encapsulant 2 has cured, the profiling blade 30 moves across the die 4 and wire bonds in a predetermined path. As shown in FIG. 3B, the blade 30 displaces the top of the bead 30 to its flex PCB side to form a flat top surface 32 that is at a significantly reduced height H above the die 4.

The encapsulant bead 2 may be a plurality of separate beads as shown in FIGS. 1 and 2, or a single bead of one material. However, for close dimensional control of the profiled encapsulant, the encapsulant materials used should be thixotropic—that is, once deposited from the discharge needle, or profiled by the blade 30, the material should not flow under its own weight, but rather hold its form until it cures. This requires the epoxy to have an uncured viscosity greater than about 700 cp. A suitable encapsulant is DYMAX 9001-E-v3.1 Chip Encapsulant produced by Dymax Corporation with a viscosity of approximately 800 cp when uncured. The blade 30 may be ceramic (glass) or metal and preferably about 200 microns thick.

It will be appreciated that the relative movement of the blade 30 and the die 4 can be precisely controlled. This allows the height H to be determined by the tolerance of the wire bonding process. As long as H is greater than the nominal height of the wire bond arc above the die, plus the maximum tolerance, the encapsulant 2 will cover and protect the wire bonds 16. With this technique, the height H can be easily reduced from 500-600 microns to less than 300 microns. If the heights of the wire bond arcs are also reduced, the height H of the encapsulant bead can be less than 100 microns. The Applicant uses this technique to profile encapsulant on print head dies down to a height of 50 microns at its lowest point. As shown in FIG. 3C, the lowest point is at the encapsulant front and the blade 30 forms an inclined face 32 in the top of the bead 2. The inclined face is utilized by the print head maintenance system when cleaning the paper dust and dried ink from the nozzle face. This illustrates the technique's ability to not just reduce the height of the encapsulant bead, but to form a surface that can perform functions other than just encapsulate the wire bonds. The edge profile of the blade and the path of the blade relative to the die can be configured to form a surface that has a multitude of shapes for a variety of purposes.

Plastic Deformation of the Wire Bond Arcs

FIGS. 4A to 4C show another technique for lowering the profile of wire bonds. FIG. 4A shows the die 4 connected to the flex PCB 8 via the wire bonds 16. While the stepped support structure 6 has lowered the height of the wire bond arcs compared to a flat supporting structure, the wire bonds still have a natural tendency to bow upwards rather than downwards towards the corner of the step. The wires 16 are typically about 32 microns in diameter and have a pull force of about 3 to 5 grams force. The pull force is the tensile load necessary to break the connection to the contact pad 10 or the bond pad 12. Given the fragility of these structures (one of the reasons encapsulant is applied), conventional wisdom is to avoid any contact between the wire bond arcs and other solid surfaces.

As shown in FIG. 4B, the arc of the wire bonds 16 can be collapsed by a wire pusher 34. The wire pusher 34 displaces the wire bond 16 enough to elastically and plastically deform the arc. The Applicants have shown that contact with the wire pusher 34 can cause localized work hardening in the wire, but as long as the pushing force is not excessive, it does not break. The end of the wire pusher 34 is rounded to avoid stress concentration points. The wire pusher may be a stylus for engaging single wire bonds or a blade that pushes on multiple wire bonds simultaneously.

Referring now to FIG. 4C, the wire pusher 34 is retracted and the wire springs back toward its original shape to relieve the elastic deformation. However, the plastic deformation remains and the wire bond height above the die 4 is much reduced. Testing has shown that an initial wire bond loop height of 200 microns can be reduced to about 35 microns using this technique. Tests have also shown that the pull strength of the plastically deformed wires remains at about 3 to 5 grams force.

The collapse of the wire bonds is uncontrolled and leaves the wire bonds somewhat randomly deformed. However, pushing the wire bonds closer to the die provides more uniformly shaped collapsed wire bonds. The Applicant's work has shown that engaging the wires about 200 to 300 microns for the die provides the best results.

As shown in FIG. 4D, the die 4 and the flex PCB 8 are mounted to a flat support structure 6. As discussed above, this means the original loop height of the wire bond arc is much higher—approximately 400 microns above the die 4. Consequently, the wire has more plastic deformation when the loop is collapsed by the wire pusher. Even so, the Applicants results show that the residual loop height after pushing is about 20-50 microns.

FIGS. 5A and 5B show the collapsed wire bonds 16 covered with an encapsulant bead 2. Even without bead profiling prior to curing, the height H of the bead above the die is much less than the bead necessary to encapsulate the original undeformed wire loops.

Applying Encapsulant with Profiling Blade

FIGS. 6A, 6B and 6C show the application of the encapsulant bead using the profiling blade 30 instead of a discharge needle (see FIGS. 1 and 2). As previously discussed, the flowrate of encapsulant from the discharge needle can vary and this gives rise to large variations on the position of the encapsulant front on the active surface of the die 4. Consequently, any functional elements in the active surface of the die need to be sufficiently spaced from the contacts pads 10 to allow for the meandering encapsulant front.

Applying the encapsulant with the profiling blade avoids the problems caused by the flowrate fluctuations from the discharge needle. As shown in FIG. 6A, the bead of encapsulant 40 can be formed on the profiling blade 30 by simply dipping it into a reservoir of uncured encapsulant epoxy. Of course, the bead 40 may also be formed by any other convenient method, such as running the discharge needle along one end of the blade 30.

FIG. 6B show the blade 30 having been lowered to touch the bead 40 onto the die 4. When the encapsulant material touches the die surface, it wets and wicks along the surface while remaining pinned to the edge of the blade. The blade 30 is held at a predetermined height above the die 4 and moved over the bead 2 to flatten and lower its profile. The encapsulant displaced from the top of the bead 2 by the blade 30, spreads over the PCB side of the bead 2. It is not relevant if the encapsulant spreads further over the PCB than necessary. As long as the wire bonds 16 and the bonds pads 12 are covered, any additional encapsulant on the PCB 8 surface is not detrimental.

In FIG. 6C, the wire bond 16 height has been reduced by collapsing the arc in accordance with the techniques discussed above. As previously discussed, the bead 2 deposited by the discharge needle need not be as big to cover the wire bond 16 once it has been collapsed. Furthermore, the blade 30 can be brought closer to the die 4 without contacting wire bonds 16 when profiling the encapsulant 2. Hence the bead profile in FIG. 6C is substantially lower than that of FIG. 6B.

Encapsulant Front Control

When the encapsulant material is dispensed from the discharge needle, minor variations in the flowrate can cause the bead to bulge at points of higher flow. Consequently, the side of the bead that contacts the active surface of the die is not straight, but has significant perturbations. These perturbations have to be accommodated between the contact pads and any functional elements on the active surface. The spacing between the contacts pads and the functional elements consumes valuable ‘chip real estate’. The Applicant has previously developed print head dies with a spacing of 260 microns between the contact pads and the first row of nozzles. Better control of the encapsulant front reduces the space between the contacts and operational elements, and so the overall dimensions of the die. Hence the design can be more compact and more chips fabricated from the original wafer disc.

As shown in FIGS. 7A and 7B, the profiling blade 30 is used to control the front 36 of the bead of encapsulant 2. The blade 30 is positioned over the die 4 to define a gap 42 between its lower edge and the active surface 28. As the discharge needle 18 dispenses the encapsulant material 44, it flows onto the active surface, one side of the blade and a fillet of the material extends through the gap 42. Because of the flow restriction created by the gap, flow variations have a reduced effect on the dimensions of the fillet that flows through the gap. Therefore the encapsulant front 36 closely corresponds to the line of the lower edge of the blade 30.

As shown in FIG. 7B, the profiling blade 30 is already in position to profile the encapsulant bead 2 once it has been dispensed from the discharge needle. The blade 30 simply moves over the die 4 in a direction away from the nozzles 38. This keeps the encapsulant front 36 in place and flattens the profile of the encapsulant bead 2 over the wire bonds 16.

Collapsing the Wire Bonds Arcs with the Wirebonder

FIGS. 8 and 9 show a technique for individually deforming each of the wire bond arcs using the wire bonder. This has several advantages over the technique shown in FIGS. 4A to 4C described in the “PLASTIC DEFORMATION OF THE WIRE BOND ARCS ” section above. Firstly, deforming the wire bonds as they are being attached by the wire bonder is more time efficient than pushing the line of wire bonds as a separate production step. Secondly, it has been found that individually engaging and deforming each wire in the line of wire bonds provides uniform results in terms of wire deformation and bond strength.

FIG. 8 is a schematic perspective of a wire bonder 46 forming the individual wire bonds 16 between the contact pads 10 and the conductors 12 on the flex PCB 8. The print head IC 4 is shown adhered to one side of the die attach film 58. In turn, the die attach film 58 is attached to the LCP molding 6. Laser ablated holes through the die attach film 58 feed ink to the array of nozzles 38. The LCP molding six has a stepped surface 60 so that the print head IC 4 is raised relative to the flex PCB eight. As discussed above this helps to reduce the height of the wire bonds 16.

The wire bonder 46 is commonly known in the industry as a “wedge type” wire bonder. The wedge 48 receives a stock of feed wire 56 at its tip. Using some combination of pressure, heat and ultrasonic energy, the end of the wire bond 16 is welded to one of the conductors 12 on the flex PCB 8, or one of the contact pads 10 on the print head integrated circuit 4. FIG. 8 includes an enlarged inset showing the connection between the wire bond 16 and the conductor 12. The end of the wire has a flatten section 54 created by the tip of wedge 48. Adjacent to flatten section 54 is a neck portion 52 where the wire 16 transitions to its circular cross section. This neck section of the wire is work hardened and particularly prone to plastic deformation. In light of the greater propensity for plastic deformation at the neck portion 52, the wire bonder 46 is fitted with a wire engaging structure 50 pushes on the wire bond 16 in this region. However, the wire engaging structure 50 to not contact the wire bonds 16 too close to the neck portion 52 is this can break the wire. The skilled worker will appreciate the work hardening increases the brittleness of the metal. The applicant's testing has found that positioning the wire engaging structure 50 so that its tip is between 1.0 mm and 1.6 mm behind the tip of the wedge (with respect to its movement from the die to the flex) and 50 microns to 600 microns below the tip of the wedge produces suitable results. In particular, the best results were achieved with the tip of the wire engaging structure 50 positioned 1.2 mm to 1.5 mm behind the tip the wedge, and 100 microns to 300 microns below the tip of the wedge. This configuration gave wire bonds 16 less than 50 microns above the nozzle array 38, each with a bond strength between 3.5 g and 5 g.

The wire engaging structure 50 is formed from a material with the surface hardness less than that of the wire. This avoids surface indentations on the wire which may later become stress concentration sites.

Adhering the Wire Bond to Reduce Loop Heights

FIG. 10 is a schematic section view of another technique used to reduce the height of the wire bond loops. An adhesive surface 62 is positioned on the LCP molding 6, between the contact pads 10 of the print head IC 4 and the corresponding conductor 12 on the flex PCB 8. The Applicant has found that a wire bonder will usually allow the wire bond 16 to drape downwards and touch the surface between the die and PCB while the wire is bonded to the PCB conductor. Once the wire has been welded to the contact pad on the die, the bonding tool draws it towards the conductors on the printed circuit board. As it is drawn across the gap between the die and printed circuit board, the wire drapes downwardly and rests on the underlying surface. Once the bonding tool has welded the other end of the wire to the conductor, and the wire clamp immediately behind the bonding tool breaks off the feed wire by pulling until tensile failure, the residual tension in the loop cause it to bow upwards. By positioning adhesive 62 at the point of contact between the wire and the LCP 6, the wire bond 16 is unable to bow upwards to the same height.

The adhesive surface 62 may be double sided tape, an adhesive paste or resin jetted onto the LCP 6 when the die 4 and the flex 8 are fixed, or it could simply be an extension of the die attach film 58.

The invention has been described herein by way of example only. The ordinary will readily recognize many variations and modifications which do not depart from the spirit and scope of the broad inventive concept. 

1. A method of profiling a series of wire bonds between a line of contact pads on a die, and a corresponding set of conductors on a supporting structure, the method comprising the steps of: electrically connecting each of the contact pads on the die to a corresponding conductor on the supporting structure with a respective wire bond, each of the wire bonds extending in an arc from the contact pad to the conductor; and, pushing on each of the wire bonds individually to collapse the arc and plastically deform the wire bond such that the plastic deformation maintains the wire bond in a flatter profile shape.
 2. A method according to claim 1 wherein adjacent wire bonds in the line of wire bonds are sequentially pushed.
 3. A method according to claim 1 wherein the step of forming the line of wire bonds uses a wire bonder that has a bonding tool for moving between the contacts pads and their respective corresponding conductors, and the line of wires bonds are sequentially pushed by a wire engaging structure on the wire bonder.
 4. A method according to claim 3 wherein the wire engaging structure and the bonding tools are configured for synchronized movement.
 5. A method according to claim 4 wherein the wire engaging structure pushes the wire bond immediately adjacent the wire bond currently being formed by the bonding tool.
 6. A method according to claim 1 wherein the wire bonder is a wedge type wire bonder and the bonding tool is a wedge such that during use, the wedge holds a piece of wire in contact with one of the contact pads on the die to form a weld connection before moving to the corresponding conductor on the PCB to weld the other end of the wire and formal wire bond, and the wire engaging structure has a wire pushing surface that contacts the wire bond, the wire pushing surface is adjacent to, and 1.0 mm to 1.6 mm behind the wedge with respect to the movement of the wedge towards the IC die.
 7. A method according to claim 6 wherein the wire pushing surface is between 50 microns to 400 microns closer to the PCB than the wedge.
 8. A method according to claim 1 wherein the line of wire bonds does not extend more than 150 microns above the contact pads of the IC die.
 9. A method according to claim 8 wherein the line of wire bonds does not extend more than 50 microns above the contact pads of the IC die.
 10. A method according to claim 1 wherein the wire bonds are attached to the contact pads with a bond strength greater than 3 g force.
 11. A method according to claim 1 wherein the contact pads are spaced from the corresponding conductors on the PCB by more than 1 mm.
 12. A method according to claim 11 wherein the contact pads are between 2 mm and 3 mm from the corresponding conductors on the PCB.
 13. A method according to claim 1 wherein the PCB is a flexible PCB mounted to a support structure together with the die such that the conductors are adjacent the contact pads on the die.
 14. A method according to claim 13 wherein the support structure has a chip mounting area for supporting the die, the die having a back surface in contact with the chip mounting area and an active surface opposing the back surface, the active surface having the contact pads, and the chip mounting area being raised relative to the remainder of the support structure such that the contact pads are raised relative to the conductors.
 15. A method according to claim 14 wherein the support structure is a liquid crystal polymer (LCP) molding.
 16. A method according to claim 14 wherein the active surface has functional elements spaced less than 260 microns from the contacts pads of the die.
 17. A method according to claim 16 wherein the die is an inkjet print head IC and the functional elements are nozzles through which ink is ejected.
 18. A method according to claim 15 wherein the wire bonds are covered in a bead of encapsulant, the bead of encapsulant extending less than 200 microns above the active surface of the die.
 19. A method according to claim 18 wherein the wire bonds are covered in a bead of encapsulant, the bead of encapsulant having a profiled surface that is flat, parallel to and spaced less than 100 microns from the active surface.
 20. A method according to claim 17 wherein the print head IC is mounted in a printer such that during use the nozzles are less than 100 microns from the paper path. 